# CVE-2021-39341: OptinMonster <= 2.6.4 Unprotected REST-API Endpoints

- Exploited (CISA KEV): no
- Published: 2021-11-01
- CVSS: 8.2 HIGH (v3.1)
- EPSS: 21.9% (98th percentile)
- CWE: CWE-285, CWE-319

The OptinMonster WordPress plugin is vulnerable to sensitive information disclosure and unauthorized setting updates due to insufficient authorization validation via the logged_in_or_has_api_key function in the ~/OMAPI/RestApi.php file that can used to exploit inject malicious web scripts on sites with the plugin installed. This affects versions up to, and including, 2.6.4.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Before feed history | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | Before feed history | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2025-08-15 | 1383 |
| Akamai | No public source | — | — |
| OWASP CRS | Before feed history | — | — |

### F5

- 2025-08-15 · new · rule 200009335
  > Added: signature 200009335 "WordPress OptinMonster Information Disclosure" (Information Leakage, risk Medium), systems: WordPress. References: CVE-2021-39341.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: blocked (1 of 1 requests blocked), template CVE-2021-39341, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: blocked (1 of 1 requests blocked), template CVE-2021-39341, 2026-11-02

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2021-39341 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2021-39341